That is not a flagrant foul, it's a technical foul. LeBron instigated the altercation with the take down and step-over, and Green re-acted. Textbook definition of a situation that normally warrants a double-tech, one assessed to each player.
Had the refs done job their game during the game when this actually happened, and issued the infamous double-tech, nobody says anything further and no suspension happens.
Instead, here we are in a world where Green is improperly suspended for a Finals game, because the league didn't want to look like they keep letting Green get away with nut shots. Meanwhile, LeBron still instigated the whole matter.
But I don't feel sorry for Green, maybe his teammates, but not Green. Green is a dirty player. That's the price you pay for crossing the line one too many times.